1. Field of the Invention
The present invention relates generally to a signal lamp composed of a plurality of light emitting diodes for a vehicle. More particularly, the present invention relates to a signal lamp for a vehicle, e.g., a motorcar composed of a plurality of dome type light emitting diodes and a plurality of reflective mirrors arranged corresponding to the light emitting diodes (LEDs) wherein the signal lamp is employed for a brake lamp and each light emitting diode serves as a light source.
2. Description of the Related Art
FIG. 3 is a sectional view which illustrates the foregoing kind of conventional signal lamp 31 for a vehicle composed of a plurality of light emitting diodes and a plurality of reflective mirrors arranged corresponding to the light emitting diodes. The conventional signal lamp 31 is constructed such that a plurality of light emitting diodes 32, each including a so-called dome type light emitting diode chip 32a which is sealably received in a substantially cylindrical transparent case 32c molded of synthetic resin and of which the foremost end part serves as a lens portion 32b, are arranged in an equally spaced relationship with a predetermined distance kept between the adjacent LEDs, a plurality of reflective mirrors 33 each having a focus located at the light emitting diode chip 32a are disposed behind the respective light emitting diodes 32 and a lens 34 transversely extends in front of the respective light emitting diodes 32 and the reflective mirrors 33 to cover them therewith.
With the conventional signal lamp 31 as constructed in the above-described manner, properties of light emitting and reflecting are determined mainly depending on the lens portions 32b of the cases 32c. Thus, a principal object of each reflective mirror 33 is to emit light to the intermediate region between the adjacent light emitting diodes 32 so as to uniformly illuminate the surface of the lens 34.
However, it has been found that based on the results derived from careful examination on the light emitting diode 32, since the light emitting diode chip 32a of the light emitting diode 32 is mounted on the bottom of a dish-shaped horn portion 32e (see FIG. 4) formed on a lead frame 32d for the purpose of raising a level of efficiency, many ineffective spots appear on the reflective mirror 33 of which focus is located at the light emitting diode chip 32a, due to formation of light intercepting spots and thereby it becomes impossible to uniformly illuminate the surface of the lens 34. For these reasons, the conventional signal light 31 has a problem that brightness fluctuates over the surface of the lens 34 and thereby most of users feel unsatisfactory in respect of a quality of the conventional signal lamp.